Prosecutors in the Netherlands have filed new charges against a Dutch-born Islamic extremist who was convicted of killing filmmaker Theo van Gogh.

Mohammed Bouyeri, 27, and 12 other defendants appeared in a Dutch court Tuesday to face charges of membership in a terrorist movement authorities have called the "Hofstad Group."

The 12 defendants were arrested shortly after Van Gogh's killing.

Lawyers for Bouyeri say the prosecution wants to punish their client further, adding that he has already received the maximum sentence of life in prison. The new charges carry a maximum 15-year prison term.

Dutch authorities believe Van Gogh's murder was a response to his criticism of Islam and its treatment of women in his film "Submission."